1. Field of the Invention
The present invention relates to an optical disk, a method of manufacturing the same and a method of recording the same. More particularly, it relates to an optical disk, to which information can be recorded by a light beam.
2. Description of the Related Art
There is an optical disk reproducing apparatus as an apparatus which reproduces optical disks, such as a LD (Laser Disk) and a CD (Compact Disk). This kind of optical disk reproducing apparatus irradiates a light beam to the optical disk and reproduces information recorded on the optical disk on the basis of the reflection light from the optical disk. FIG. 1 indicates a relationship between the pit and a reflection coefficient in an ordinary disk.
In FIG. 1, a recording surface of an ordinary LD is partially shown at the lower half of the figure, while the reflection coefficient corresponding to the recording surface is shown at the upper half of the figure. Each of track portions 10 is disposed in the direction of the track. Pits 10a and 10b, which indicate information, are formed on each of the track portions 10. Each area between adjacent track portions 10, is a flat interval portion (land portion) 12. Here, a reflection coefficient (an amount of returned light) of each portion, is considered. The reflection coefficient of the track portions 10 is low due to the refraction of the light beam by the pits 10a and 10b (As indicated by the reference numeral 11L). On the other hand, the reflection coefficient of the interval portions 12 is high due to the reflection of the light beam (as indicated by the reference numeral 13H).
In the reproducing apparatus for the ordinary LD, the tracking control is performed by use of the above mentioned difference in the reflection coefficient, so as to adjust the light beam to each of the track portions 10 having the low reflection coefficient. Namely, in the tracking control by the three beam method, the reflection coefficient of the interval portions 12 having no pit, and the reflection coefficient of the track portions 10 are compared with each other, and the portion having the low reflection coefficient is recognized as the track portion 10. Thereby, the light beam is adjusted to the track portion 10.
In the above mentioned ordinary LD, the information is recorded beforehand. On the other hand, there is a recordable optical disk onto which a user can record information arbitrarily. There is a Recordable-LD described as a R-LD, which is an example of such a recordable optical disk.
In the R-LDs using the dye of phthalocyanine series and cyanine series as a recording layer, there is a R-LD which high and low reflection coefficients are opposite to that of the above mentioned ordinary LD. Namely, at the track portion, the reflection coefficient is high, while at the interval portion between two adjacent track portions, the reflection coefficient is low. This feature is explained with reference to FIG. 2.
FIG. 2 indicates a relationship between the pit and the reflection coefficient in such a R-LD. At the track portions 10 having pit 10a and 10b, the reflection coefficient (amount of the return light) is high (as indicated by the reference numeral 11H). On the other hand, at the interval portions 12, the reflection coefficient is low (as indicated by the reference numeral 13L). Therefore, when the tracking of the light beam is carried out, it becomes necessary to adjust the light beam to the track portions 10 having the high reflection coefficient. This tracking characteristic is contrary to that of the ordinary LD of FIG. 1. For this reason, the R-LD cannot be reproduced by the reproducing apparatus for the ordinary LD. In order to reproduce the R-LD, it becomes necessary to invert the tracking characteristic within the reproducing apparatus.